У вашего броузера проблема в совместимости с HTML5
This short video explains how you can use the JS debugger keyword to launch the debugger interface in the browser and then use the Watchlist and breakpoints to inspect your code and find problems.
Code GIST: https://gist.github.com/prof3ssorSt3v3/376605e2ed7ada56991ceb9413ddb0fd